We propose a novel nonorthogonal multiple access (NOMA) scheme referred as adaptive constellation multiple access (ACMA) which addresses key limitations of existing NOMA schemes for beyond 5G wireless systems. Unlike the latter, that are often constrained in choices of allocation of power, modulations and phases to allow enough separation of clusters from users combined signals, ACMA is power, modulation and phase agnostic forming unified constellations instead where distances of all possible neighbouring points are optimized. It includes an algorithm at basestation (BS) calculating phase offsets for users signals such that, when combined, it gives best minimum Euclidean distance of points from all possibilities. The BS adaptively changes the phase offsets whenever system parameters change. We also propose an enhanced receiver using a modified maximum likelihood (MML) method that dynamically exploits information from the BS to blindly estimate correct phase offsets and exploit them to enhance data rate and error performances. Superiority of this scheme, which may also be referred to as AC NOMA, is verified through extensive analyses and simulations.

翻译：本文提出一种新型非正交多址接入（NOMA）方案——自适应星座多址接入（ACMA），该方案解决了超5G无线系统中现有NOMA方案的关键局限性。与现有方案通常受限于功率、调制及相位分配以保障用户组合信号的簇间充分分离不同，ACMA摒弃对功率、调制和相位的依赖，通过构建统一星座来优化所有相邻点间的距离。该方案包含基站（BS）端的一项算法，用于计算用户信号的相位偏移，使得组合后的信号在所有可能取值中获得最优的最小欧氏距离。当系统参数发生变化时，BS可自适应调整相位偏移。此外，本文还提出一种增强型接收机，采用改进的最大似然（MML）方法，动态利用BS信息盲估计正确相位偏移，从而提升数据传输速率与误码性能。通过广泛分析与仿真验证，该方案（亦可称为AC NOMA）具有优越性。